Fuel burner systems for use in furnaces, boilers, water heaters etc. are well known in the prior art. One type of fuel burner is an oil burner, and is employed in various types of apparatus, such as boilers, furnaces, water heaters, etc. In such applications, an oil burner receives a fuel oil and initiates combustion thereof to generate heat which is then employed in various manners to perform work. Although several types of oil burners exist, one exemplary oil burner is illustrated in prior art FIG. 1, and is designated at reference numeral 10. The oil burner 10 comprises a blower housing 12 having an air tube 14 extending therefrom. The air tube 14 contains a combustion head affixed or positioned at one end 16 of the air tube opposite the housing 12, the end 16 having a nozzle and electrode assembly (not shown) positioned thereat. The nozzle is coupled to a fuel pump 18 by a fuel or nozzle line (a portion of which is highlighted at 20) for delivery of fuel oil thereto. The electrode assembly in the air tube 14 is coupled to a transformer or other type ignition device 22 residing on a top portion 24 of the housing 12.
As seen in prior art FIG. 2, the fuel pump 18 is axially driven by a drive shaft 26 associated with a motor 28 located on an opposite face 30 of the housing 12. The drive shaft 26 also drives a blower wheel 32 within the housing 12 for providing air into the air tube 14 for combustion via an air inlet portion 33 in the housing 12. The motor 28 is controlled by an electronic control module 34. The electronic control 34 operates to initiate delivery of oil, air and spark to the ignition head at 16 based on a call for heat from a thermostat (not shown), for example. The controller 34 may also operate to re-initiate ignition if combustion is discontinued unexpectedly and may further discontinue delivery of oil to the nozzle if ignition cannot be re-established within a predetermined lock-out time period (sometimes referred to as a safety lock-out condition).
Various types of controllers exist for oil burners. The controller 34 illustrated in prior art FIGS. 1 and 2 represents one basic type of controller that is used extensively. The controller 34 initiates air flow and fuel delivery substantially simultaneously via the motor drive shaft, while concurrently initiating spark at the head via a signal to the transformer 22. A flame detector such as a cad cell views the combustion area to determine whether or not combustion has occurred. The controller 34 receives a signal from the thermostat and acts to control the operation of the oil burner 10. More particularly, when the thermostat sends a signal calling for more heat, the controller sends a signal to the igniter 22 that then operates to produce a spark across the gap between the electrodes. The controller 34 also sends a signal to energize the motor 28, the blower 32 and the pump 18 to start the mist of oil and air flowing from the blower section to the combustion chamber. If the oil and air are present and the spark ignites the oil, then the flame detector provides a signal to the controller 34 to indicate that satisfactory combustion has occurred. Thereafter, the igniter 22 turns off (referred to as “interrupted” operation) and the furnace produces heat until the call for heat is lost and the motor 28, the pump 18 and the igniter 22 are shut off.
In a normal operation of the system, when a call for heat is identified from the thermostat, the controller 34 starts the ignition process, wherein flame is established and the system enters a run mode or run state. In the run state the furnace supplies heat until the call for heat from the thermostat disappears. Sometimes in the normal run state, the flame can go out before the call for heat from the thermostat ends. This condition is sometimes caused by a transitory condition such as an air bubble in the fuel line. When the flame in the burner goes out after having been established and before the thermostat stops calling for heat, the system goes into a recycle mode which, after a delay (recycle time), the system reverts to an initial state. In this initial state, since the controller 34 still receives the continued call for heat from the thermostat, the controller 34 starts the ignition process and again attempts to initiate a flame. If successful the system then returns to its normal run state. Unfortunately, the condition causing the loss of flame condition may not have disappeared; for example, when the system does not support combustion after the igniter 22 turns off. When this occurs, the flame will again extinguish, thus putting the system back in the recycle mode again and an endless cycle to the run mode and recycle mode may occur. This endless recycling is often due to a poor combustion situation and thus excessive soot may develop, excessive wear on components may result, and other damage may occur.
One prior art controller addressed the potential problems associated with the endless recycle condition by limiting a number of recycle attempts to a predetermined number, after which the system entered a lockout state. It is always desirable to provide further improvements in controller devices and methodologies.